This is anoying the Device runs alone very well, no problems...

As you can see:
http://www.vartaleaks.com/chipdac-metal.mp4

i use a simple Amp:
https://english.electronica-pt.com/db/images/TDA7050.jpg
Added 100nf and 10uf as deblocking.

Unfortunaly i did not paint a Schematic for now.
Only soldered on protoboard.

http://www.epanorama.net/circuits/dacs.html

its combined with this Schematic:
http://www.epanorama.net/circuits/cent_dac.gif

Circuit is driven from 9V Lab Power Supply or 9V Batterie (For mobile usage)
VIA 7805 with 2x 100nf and 2x 10uf Deblocking on in and output.

As you can hear above, its working glad and has no issues on every computer i tried (at least 4)
Only one older Laptop is not working, LPT has not much driving Power and with 74HC244 added it works.

matze79 wrote:

2017-12-09 (1).png

😒 from Amp Output, also happens without Amp (only when DSS is not active)

Very nice. So. Definitely 50 Hz, highly structured, and also sub structured.

Update:
The DAC does not like having Inputs float.
Adding a Bus Driver solved one of the problems for me.
At least my perfboard build is working now.

The DSS has still some noise on it 😒

I have 5 DSS Boards left, if anyone is intressed just write me a PM.

please tell me the "simplest" way for the getting voltage? Thx Doc

Just pass 5V to the 2 Pin Header, maybe from Computer Powersupply Molex connector ?

3,5" Floppy Connector maybe ^^

USB-Solution possible? I want to use this machine: https://images-na.ssl-images-amazon.com/image … 41DAtN5PqzL.jpg

Thx!

You can also use USB, do you have some old USB Cable ?
just strip it and connect Redwire near the Diode and Blackwire next to R1 on the Jumperheader.

I should have some USB-Cables 😀

Simple Covox Device:

Schematic and BRD included.

If anyone needs it, simple order at oshpark.com or dirtypcbs.com 😀
Or etch one. Yeah i know it could be easily build without PCB.
But this will allow faster production. Simply print 10 and etch.

You may want to choose your own Output Capacitor.

i also did a new PCB Design for DSS. But currently somehow busy..
Expect a Update in next months for a 50Hz Buzz Free DSS.

EDIT:
Both PCBs can be panelized to order them as One.

nice !

Nothing special 😀

So I take it the thing pictured on the right: https://i.imgur.com/2FxAIoN.png is just a plastic case housing a speaker and volume knob?

As far as i known the whole DSS is inside the Plug.

The other Case just contains a Amp and the Volume knob right ?

^ yes exactly the housing is a speakerphone, an amp and the 9v battery storage.
The DSS circuitry is in the silver lpt housing:

I will post a pic of the speakerphone if I find it 🤣

edit: here it is

*Bump*

Has anyone of you attempted to make my layout compatible for switching between DSS and Covox modes?
I'm currently contemplating various implementations (ranging from hackjob to textbook example), maybe some of you have made some observations I'd love to hear about.

EDIT: Hackjob apparently works (was worrying if the FIFO outputs maybe didn't like having signals banged onto them). You need a 74LS245 to completely bypass the DSS specific logic (connect datalines from one dsub 25 to another) and a dual 2 way switch. One path for enabling/disabling the 74LS245, the other for setting the FIFO into a permanent Reset/Output disabled state.
EDIT2: https://i.imgur.com/ah9chkx.jpg (yes, that's on original, vintage, r@re l@@k c64 power switch)

Did some testing on breadboard with few 74hc244's, did work fine but have not yet made any further progress..

anyway we started using a atmega88 and using internal timer and some buffers in memory for emulating the fifos,
instead of r2r ladder, pwm is used.
but my friend had no time to continue this effort, job and family also needs attention and i'm not a very good programmer 😒

keropi wrote:

^ yes exactly the housing is a speakerphone, an amp and the 9v battery storage.

I'm not sure what you mean by speakerphone. I guess you plug a phone into it and it outputs to the speaker instead of the phone handset? Odd misplaced feature for a kids sound device, I wonder what use case they had in mind. Looks like the circuit board has a headphone pass through as well?

I think he meant loudspeaker

Just thinking at the moment ... what would you say about having a multi-mode covox that's switchable by software?

Benefit: No more climbing under the table to change modes between DSS and Covox
Drawback: Being dependant on a small piece of software (I guess MSDOS would be sufficient, I can set the hardware to default to a certain mode on powerup)